Heat storage material

ABSTRACT

A liquid melt becomes converted to crystalline form at a particular temperature either spontaneously or when artificially nucleated. The liquid releases heat at crystallization. If the liquid is in a supercooled state when it begins to crystallize, its temperature will rise from the particular temperature at which it is nucleated. 
     Another liquid material is mixed with the liquid to be crystallized. The liquid additive has properties of forming a metastable solid together with the crystallizing material. When the liquid additive exsolves, the crystalline aggregate is weakened and is easily decomposed into fragments of small size. The liquid additive materials may include monohydric alcohols, diols and triols. The liquid additive material may be included in the liquid to be crystallized, in small amounts, amounts to two percent (2%) to five percent (5%) being typical. The amount and relative metastability of the liquid additive material in the solution contributes to control of the size of the crystals which are ultimately produced when the supercooled fluid crystallizes. A small amount of surface active material may also be included to modify the characteristics of the metastable solid solution, the exsolution process, and the texture of the exsolved crystal aggregate.

This invention relates to recyclable hot pads or containers forgenerating heat at a controlled temperature for extended periods oftime. More particularly, the invention relates to hot pads in which thematerial in the pads is provided in a form during the generation of heatsuch that the pads can be comfortably applied to the body of a patientfor an efficient transfer of heat to the patient's body. The inventionalso relates to a method of forming such pads.

As medical science becomes advanced, it is increasingly important toapply heat at controlled temperatures to a patient for extended periodsof time in order to optimize the beneficial effects of such heat on thepatient. For example, it is often difficult to obtain blood from a babyfor performing tests on the baby. It has been found that blood can bewithdrawn most easily from the heel of a baby, particularly when theheel has been heated to a particular temperature. Since the baby cannotexpress in any easily identifiable way when the heat becomes excessive,babies sometimes become burned by the application of excessive heat.

As another example, it is often desirable to dispose a baby on amattress which has been heated to a particular temperature. The mattresshas to be comfortable to the baby at the same time that heat is beingapplied at the particular temperature to the baby. For example, themattress should not be lumpy or provide sharp projections since thelumps or sharp projections affect the comfort of the baby.

Preferably the heat pads or containers should be recyclable. In otherwords, the pads should be capable of being used more than once togenerate heat at the particular temperature. In this way, the cost ofthe pads can be amortized over a number of uses so that the cost per useis relatively low.

Heat pads have been provided in the prior art which meet a number of theobjectives discussed above. For example, heat pads have been providedwhich are able to operate on a recyclable basis. Such heat pads haveused supercooled melts which are nucleated at a particular temperatureto become crystallized and to generate heat as the melts crystallize.Such heat pads employing supercooled liquid melts have been recyclablesince the crystalline solid can be heated at the particular temperatureto change the crystals to liquid state and the liquid state can then beretained in a metastable form at temperatures below the particularmelting temperature. However, it has been difficult to provide for thematerial a melting temperature which provides optimal results. Forexample, when the material is to be used as a hot pack for babies tofacilitate the withdrawal of blood from the babies, a meltingtemperature of approximately 104° F. for the crystalline solid isconsidered as optimal. Such a temperature has been difficult to obtainin a heat pack having the desired metastable characteristics.Furthermore, it has been difficult to inhibit the spontaneouscrystallization of the supercooled melts at low temperatures such astemperatures below 32° F.

It has also been difficult to provide the crystals with a uniformlysmall size. It has further been difficult to provide the crystals with asize which is predetermined in accordance with the use to be made of thecrystals. For example, crystals of one size may be desired for heel padsfor babies and crystals of a different size may be desired for babymattresses.

This invention provides heat pads or containers which overcome the abovedifficulties. The heat pads can be controlled to produce crystallizationof a liquid in the heat pads at any pre-selected temperature between themelting point and the temperature of spontaneous nucleation. Thecrystallization can also be controlled such that crystals in any desiredsize range can be produced. In this way, the size of the crystallitescan be adapted to the particular use that is to be made of the heatpads. As the melt crystallizes, it liberates heat so that thetemperature rises from the particular temperature to a maximumtemperature, which may coincide with, but does not exceed, the meltingtemperature. The heat pads are recyclable since they include liquidswhich become crystallized in the particular temperature range togenerate heat and which become converted back to liquid form by thesubsequent application of heat at or above the melting temperature. Themelt in the heat packs has characteristics of remaining as a liquid in ametastable form at temperatures below the particular melting temperatureuntil such time as the generation of heat is again desired.

Preferably the liquids in the heat pads of this invention aresupercooled. Different liquid phases may be used depending upon theparticular temperature interval in which the heat is to be generated.

The heat pads of this invention also include an additive liquid-phasematerial. The liquid additive material may be preferably selected from agroup consisting of monohydric alcohols, diols and triols. The liquidadditive material has properties of dissolving metastably in thecrystals and to exsolve so as to limit the ultimate size of thecrystallites. The amount and chemical properties of the liquid additivematerial in the supercooled melt contribute to control of the size ofthe crystallites that are produced when the supercooled fluid isnucleated to form one or several crystalline solids. Preferably, theamount of the liquid additive material in the supercooled melt forcontrolling the size and texture of the crystallites produced from thesupercooled fluid should not exceed approximately two percent (2%) tofive percent (5%) by weight.

It will be appreciated, however, that amounts of the liquid additivematerial in excess of two percent (2%) to five percent (5%) may beincluded in the liquid melt, particularly when it is desired to controlthe amount of heat generated by the melt. Under some circumstances, anamount of liquid-phase material in excess of two percent (2%) to fivepercent (5%) in the liquid melt may be advantageous in controlling thesize and texture of the crystallites.

The liquid-additive material is also advantageous in controlling theparticular maximum temperature which the supercooled melt reaches atcrystallization. When the liquid additive material is used to providesuch control of the melting temperature interval, it may exceed thepreferable criterion of two percent (2%) by weight specified above,depending upon the particular temperature desired. The liquid additivematerial is also advantageous in inhibiting the uncontrolled andunintended spontaneous nucleation of the supercooled melt into incipientcrystallization at low temperatures such as temperatures in the range of0° F. to 35° F. Such control over such unintended nucleation intocrystallization of the supercooled melt is especially important when theheat pads are shipped to distant destinations through winter climateswith the melt in a supercooled state.

The effect of the liquid additive material in limiting the size of thecrystals results from two different but related actions of the liquidadditive material. In one action, the liquid additive material adsorbsto specific surfaces of the crystals so as to inhibit their growth. Inanother action, the adsorbed liquid additive material forms a metastablesolid solution or dispersion in the crystals. This metastable solutionor dispersion subsequently exsolves to form oriented vesicular liquidinclusions, which weaken the crystals and cause the crystals to break.The liquid inclusions also tend to cluster together and grow in size andthereby contribute to breaking up the crystals into fragments. Thesefragments can be given various sizes in the overall range of the orderof ten (10) to one thousand (1,000) micrometers (μm) with consistencycorresponding to that of sand or silt. If the heat pad is gentlyagitated as the crystals form, the achievement of this ultimateconsistency is accelerated.

The heat pads may also include a small amount of a surface activematerial which is provided with properties of lowering the surfacetension of the crystals produced from the melt such as the supercooledmelt. The surface active material may be selected from a groupconsisting of sulfates, phosphates, phosphonates and sulfonates. Thesurface active material is preferably used when the liquid phasematerial constitues particular ones of the liquid phase materials suchas monohydric alcohols.

When the surface active material is used, the characteristics of thesurface active material modify the rate of absorption and occlusion ofthe liquid additive. As a result, the texture of exsolved crystalsaggregate, and the crystallites, can be modified beyond the limitsimposed by the liquid additive. In those cases where the liquid additivehas a limited solubility in the melt, such as in the case of certainmonohydric alcohols as liquid additives, the use of appropriate surfaceactive agents contributes to the stabilization of the liquid additive asa colloidal suspension in the melt.

The ability of the surface active material to affect the texture of thecrystalline solids results from certain characteristics of suchmaterial. For example, the surface active material characteristicallyconsists of longchain molecules with the terminal group on one end ofthe molecule having a high affinity for one or several of the componentsof the supercooled melt, and the other end having an affinity for theliquid additive. The distribution of the surface active material at thephase boundary between the supercooled melt and the liquid additivephase changes the surface energy of the system and causes the liquidadditive to enter the supercooled melt, and the crystals forming fromthe melt, in a colloidal suspension. This colloidal suspension, whenoccluded in the crystalline phase, is in a metastable state, and tendsto coalesce into larger exsolution vesicles, oriented on preferredcrystallographic planes. The formation of these oriented exsolutionvesicles weakens and disrupts the crystals so as to form smallcrystallites of size and shape dependent upon the combination of liquidadditive material and surface active material on one hand andsupercooled melt material on the other.

As will be seen from the above discussion, the use of a liquid additivematerial alone or the combination of a surface active material and aliquid additive material in a mixture with a heat-generating materialsuch as a supercooled melt constitutes one feature of this invention.This combination provides a distinct advantage over such prior art asU.S. Pat. No. 3,770,390 issued to Teet on Nov. 6, 1973 and U.S. Pat. No.3,653,847 issued to Abelson on Apr. 4, 1972, since neither of thesepatents discloses or contemplates the inclusion of additional materialinto a liquid such as a supercooled melt to limit the size of thecrystals produced from such a melt.

In the drawings:

FIG. 1 is a side elevational view of a hot pad of the present inventionwhen used as a baby mattress;

FIG. 2 shows in an exploded perspective relationship, partially brokenaway, the different members included in the baby mattress of FIG. 1;

FIG. 3 is a sectional view of the baby mattress of FIGS. 1 and 2 andillustrates the relative size of the crystals produced in such amattress when the liquid melt in the mattress crystallizes to generateheat;

FIG. 4 is a side elevational view, partially broken away, of a heel padapplied to a baby to facilitate the withdrawal of blood from the baby;and

FIG. 5 is a perspective view, partially broken away, of the heel pad ofFIG. 4 when applied to the heel of a baby.

In one embodiment of the invention, a hot pack includes a liquid meltpreferably having supercooled properties. A supercooled liquid melt hasproperties of crystallizing at a particular temperature to liberateheat. The crystallization occurs over an extended period of time,starting at the particular temperature and culminating at a temperatureat or below the melting interval of the particular phase system so thatthe particular range of temperatures is produced for the extended periodof time. When heat is subsequently applied to the resulting solid at orabove its melting temperature interval, the solid returns to a liquidform and (unless nucleated) remains in the liquid form even attemperatures below the melting temperature interval. When thesupercooled melt again becomes nucleated, it crystallizes again, whileliberating heat. In this way, the melt is able to store heat until suchtime as it is desired to liberate the heat. Furthermore, the system canbe recycled through a number of successive cycles to store and thenliberate heat.

A number of different materials can be used to store and liberate heatof crystallization. These materials are hereinafter referred to as "themelt". These materials include sodium sulfate decahydrate, sodiumthiosulfate pentahydrate (hypo), sodium chromate decahydrate, calciumchloride hexahydrate, magnesium chloride hexahydrate, magnesium nitratehexahydrate, urea/ammonium nitrate, disodium hydrogen phosphatedodecahydrate, sodium acetate trihydrate and calcium nitrate trihydrate.

A liquid additive material is included in the supercooled melt. Theliquid additive material is preferably a monohydric alcohol or a diol ora triol. When a monohydric alcohol is used, tertiary butyl alcohol orcyclohexanol are preferable. Both of these compounds, due to theirmolecular structure, have enhanced solubility in salt hydrate melts andlow surface tension relative to molten salt hydrates. When a diol isused, ethylene glycol or propylene glycol is preferred. Glycerol ispreferred when the liquid additive material is a triol.

When diols or triols are used as the liquid additive material, theliquid additive material provides an optimal effect at a concentrationby weight of approximately two percent (2%) to five percent (5%) of thesupercooled melt. In this concentration range, and below it, a majorfraction of the liquid additive material becomes occluded in thecrystals and contributes to the textural control. Below a concentrationin the supercooled melt of approximately two percent (2%), the texturaleffect of the exsolution of liquid additive material in the crystalstends to decrease. As a result, as the concentration of such liquidadditive material decreases below approximately two percent (2%), thesize of the crystallites produced by exsolution of the liquid-additivematerial, and the force needed to separate the crystallites becomeslarger. Above a concentration of approximately two percent (2%) to fivepercent (5%) by weight or volume in the supercooled melt, the liquidadditive material has only a minor added effect on the exsolutionprocess compared to that provided at a concentration in the range of twopercent (2%) to five percent (5%). Furthermore, the heat produced perunit volume of the system decreases because the liquid additive materialdoes not generate any heat when the supercooled melt crystallizes andbecause the liquid additive material in concentrations above about fivepercent (5%) causes the solidus temperature of the phase system to droprapidly. In view of this, except for special purposes, it is desirableto include as little as possible of the liquid additive material in thesupercooled melt, consistent with the amount of liquid additive materialneeded to obtain the desired textural control of the crystallinematerial formed from the supercooled melt.

As will be appreciated, the supercooled melt tends to crystallize intoone single mass or a few large masses in the heat pad if the liquidadditive material is not included. The liquid additive material tends toinhibit the formation of such a large mass or such large masses. Thisresults from the formation of absorbed layers of the additive on thesurface of the crystals as they are being formed. This thin film hasproperties which inhibit the growth of specific faces of the crystals.As a result, the crystals forced to grow by the strong supersaturationin the supercooled melt, overgrow the liquid additive, thereby causingliquid inclusions to form in the crystals. These liquid inclusionscoalesce to form laminar vesicles, intersecting segments of thecrystals. The formation of the exsolution vesicles causes the crystalsto crack and, at slight agitation, to fall apart into smallercrystallites.

The mechanical effect of exsolution on the texture of the crystalsformed at nucleation of the supercooled melt is enhanced by gentlyagitating the heat pads containing the mixture of the supercooled meltand the liquid additive material. This has the effect of acceleratingthe formation of cracks, releasing the stress on the crystallinematerial introduced by the exsolution of the liquid additive. Thus, bygently agitating the heat pad as the melt solidifies, the crystallinesolid tends to have the texture of sand or silt.

The liquid additive material contributes other important advantages whenincluded in the supercooled melt. For example, when the supercooled meltconsists of sodium thiosulfate pentahydrate, the melting temperature andhence the peak temperature of the crystallizing supercooled melt isapproximately 118° F. This temperature is higher than that desired formany applications. For example, when the supercooled melt is to be usedin heel packs for babies, it preferably should have a meltingtemperature of approximately 104° F. At this temperature, the heel packprovides an optimal effect in insuring that blood can be drawneffectively from the baby for diagnostic purposes by a heelstick. Thistemperature is also sufficiently low to prevent overheating of thebaby's skin.

The production of an optimal temperature by the nucleation of thesupercooled melt is obtained by adding a material such as propyleneglycol to the material from which the supercooled melt is produced. Forexample, when propylene glycol is added by weight in an amount ofapproximately ten percent (10%) to a supercooled melt such as sodiumthiosulfate pentahydrate, the solidus temperature decreases toapproximately 104° F. from the melting point of the pure salt hydrate at118° F. Furthermore, the resultant melt is able to exist in a liquidstate for extended periods of time at temperatures in the range down toapproximately 10° F. This is important in commercial shipments sincecrystallization of the supercooled melt would otherwise occur atapproximately 40° F. during shipment through cold climates. As will beappreciated, spontaneous crystallization of the supercooled melts in theheat packs during shipment is undesirable since it prevents the heatpacks from being used at the destination until the crystallized materialhas been recycled by melting in the case of heat packs designed forrecycling; in the case of heat packs without this provision, the damageis irreversible.

In addition to the materials specified above, other materials thenmonohydric alcohols and diols and triols may be used as the liquidadditive materials, particularly when surface active materials are alsoincluded in the system. For example, complex amines may be used.However, such materials tend to be toxic. They also tend to diffusethrough the plastic laminates used as containers in current types ofheat packs. Certain ketones (such as methyl isobutyl ketone) and esters(such as butyl phthalate, ethyl acetate and oleic acid esters) may alsobe used.

As previously described, a surface active material may be included inthe melt, particularly when the liquid additive material is a monohydricalcohol or some other compound with limited solubility in the melt. Thesurface active material is provided with properties of solubility bothin the salt hydrate melt and in the liquid-additive material and withcapability for absorption on one or several crystallographic faces ofthe salt hydrate crystals. Because of these properties, thesurface-absorption material becomes fixed to the different faces of thegrowing crystals, thereby changing the habit of the crystals and theconfiguration ratio of the exsolution vesicles forming in the crystals.In this way, the shape and separation of the ultimately forming crystalfragments, and the texture of the aggregate material, can be changed atwill within certain limits. As will be seen, the size of the moleculesof the surface active material and the structure of their functionalgroups affect the growth and combination of crystal faces. In effect,the growth of specific crystal faces is being inhibited by the additionof the surface-active materials. As a result, such faces become welldeveloped in the crystals, while fast growing faces become eliminated.

The molecules used as the surface active material may be formed aschains of atoms which may be chosen in different lengths. For example,the surface active molecules may be formed from chains of as many astwelve (12) to twenty-two (22) carbon molecules. When such long chainsof atoms are desired, the surface active materials may comprise alkylsulfates, sulfonates, phosphates or phosphonates.

The surface active material also has the properties of lowering thesurface tension between the melt phase and the liquid additive phase sothat the latter can be dispersed in the melt and stabilized there as acolloidal suspension which becomes occluded in the growing crystals andeventually exsolves to form texture-controlling vesicles in thecrystals. Preferably the surface active materials have hydrophilicproperties to accomplish this. When such properties are desired, thesurface active materials are preferably alkali salts of acids of thedesired molecular types. For example, sodium alkyl sulfate or sulfonatesmay be used. Such materials are soluble in the salt hydrate melt, andligate with the water molecules in the melt and on the surface of thesalt hydrate crystals.

Alkyl sulfates and phosphates, inorganic phosphates such aspolyphosphates, organic phosphates, phosphonates and sulfonates may beused as the surface active material. For example, lecithin (an organicphosphate) and Victawet 12 (a complex organic phosphate manufactured byVictor Chemical Company) may be used.

In addition to being soluble in water, the surface-active material maybe soluble in the liquid phase material. For example, lecithin issoluble in pentanol or amyl alcohol isomers (alcohols containing 5carbon atoms) or cetyl morpholinium ethoxy sulfate made by ImperialChemical Industries and designated by that company as Atlas G-263.

When both are used, the surface active material and the liquid additiveare included in the material such as the supercooled melt in suitableproportions. For example, approximately ten (10) milliliters of theliquid additive material and three (3) milligrams of the surface activematerial may be mixed in approximately one hundred (100) milliliters ofa melt such as the material later providing the supercooled liquid toprovide the desired result. However, as little as two (2) to five (5)milliliters of the liquid additive material may be mixed with one half(1/2) of a milligram of the surface active material in approximately onehundred (100) milliliters of a melt such as the material later providingthe supercooled liquid to obtain the desired results. Such a mixtureprovides a minimal dilution of the material to be melted andcrystallized. It also tends to insure that the temperature of themelting and crystallization of the mixture corresponds substantially tothe temperature of melting and crystallization of the pure phase orphase system used to produce the supercooled melt. For example, sodiumthiosulfate pentahydrate melts at a temperature of approximately 48° C.However, this salt hydrate with small amounts of the surface activematerial, and with two percent by weight of propylene glycol as a liquidadditive material, starts to melt at a temperature of approximately 47°C. and melts completely at a temperature of approximately 48.5° C.

Various combinations of the above materials provide particularlydesirable results. For example, cetyl morpholinium ethoxy sulfate may beused as a liquid additive material in combination with sodium laurylsulfate as a surface active material or in combination with lecithin asa surface active material; cyclohexanol may be used as a liquid additivematerial in combination with sodium lauryl sulfate dissolved inpropylene glycol, or with Victawet 11, as a surface active material;2-pentanol may be used as a liquid additive material in combination withlechithin as a surface active material; and tertiary butyl alcohol maybe used as a liquid additive material in combination with Victawet 12 asa surface active material.

The combinations disclosed above have certain important advantages. Theyprovide a crystallization of the material such as the supercooled meltas an aggregate forming small lubricated particles which provide anefficient transfer of heat to a patient or other animate or inanimateobject receiving the heat. This results in part from the fact that thecontainer holding the crystals is pliant because of the small size andmobility of the crystallites and can accordingly be bent to any desiredshape corresponding to the shape of the object to receive the heat. Forexample, when the mixture 10 is disposed in a container 12 to form aheel pad generally indicated at 14 (FIGS. 4 and 5), the heel pad can bebent into a shape corresponding to the heel of a baby so that the heatreleased during the crystallization of the material can be applieduniformly over the entire heel area of the baby.

The mixture also has certain other advantages of some importance. Forexample, the mixture 20 can be disposed in a baby mattress generallyindicated at 22 in FIGS. 1, 2 and 3 to warm a baby at a substantiallyconstant temperature for an extended period of time as the baby lies onthe mattress. By providing for the crystallization of the supercooledmelt systems into an aggregate, forming particles of a small size, themattress 22 is able to adapt to the contour of the baby so that the babycontinues to remain comfortable as heat is liberated from the mattress.

The size, shape and aggregation of the crystallites can be controlled byadjusting the concentration and composition of the liquid additivematerial in the system. For example, if the liquid additive materialforms a relatively concentrated solution in the melt, the crystallitesproduced are quite small in size. If the liquid additive material is lowin concentration, the size of the crystals becomes correspondinglyincreased. The size of the crystals may be controlled to vary frommicroscopic size through the size of sand particles to the size of largeaggregates. Furthermore, the agitation of the supercooled melt withadditives after nucleation facilitates the disruption of the crystallineaggregate, leading to the formation of a large number of small embryoniccrystals.

The systems described above can be recycled through a multiple number ofuses. For example, the baby mattress 22 described above can be providedwith a valve 40. After the supercooled melt in the mixture 20 in themattress has been produced by heating the mixture to the liquidustemperature of the systems, a nozzle 42 may be inserted into themattress to nucleate crystallization of the supercooled melt. The nozzle42 may form a part of the syringe 44 which contains a crystalline powderof sodium thiosulfate pentahydrate. This material has properties ofinitiating crystallization of the melt into the same form as thenucleating crystals as disclosed and claimed in U.S. Pat. No. 3,951,127issued to Susan Watson and William Keith Watson and assigned of recordto the assignee of record of this application.

The baby mattress 22 is preferably disposed in a cover 46, which offerscertain advantages when used with the mattress. The cover 46 may includean outer layer formed from a suitable material such as vinyl and aninner layer formed from a suitable material such as polyurethane so thatthe cover prevents diffusion of any of the compounds of the system andis pliant. In this way, the sterility of the mattress 22 can bemaintained at the same time as the baby lying on the mattress remainscomfortable. The cover 46 offers the further advantage that it limitsthe heat conductivity and thus the temperature applied to the baby ifthe temperature produced by the melt system is too high for unimpededapplication to the skin.

The following constitutes the compositions which have been treated withsodium thiosulfate pentahydrate as the supercooling material:

    ______________________________________                                        Liquid Additive                                                                            Conc.   Surface Active                                                                            Conc. Weight                                 Material     Vol. %  Material    Vol. %                                                                              %                                      ______________________________________                                        Ethylene glycol                                                                            1       --                                                       "            2       --                                                       "            3       --                                                       "            4       --                                                       "            5       --                                                       "            10      --                                                       "            2       Victawet 12 0.1                                          "            2       Victawet 12 1.0                                          Propylene glycol                                                                           1       --                                                       "            2       --                                                       "            3       --                                                       "            4       --                                                       "            5       --                                                       "            10      Victawet 12 0.1                                          "            2       Victawet 12 1.0                                          "            2       --                                                       Glycerol     1       --                                                       "            2       --                                                       "            4       --                                                       "            10      --                                                       "            2       Victawet 12 0.1                                          "            2       Victawet 12 1.0                                          Triethylene glycol                                                                         2       --                                                       1,5 pentane diol                                                                           2       --                                                       n-amyl alcohol                                                                             1.5     --                                                       "            1.5     Sodium lauryl     0.01                                                        sulfate                                                  "            1.5     Lecithin          0.1                                    "            1.5     Sodium propyl     0.01                                                        sulfonate                                                t-butyl alcohol                                                                            2       Victawet 12 1.0                                          "            2       Sodium lauryl     0.01                                                        sulfate                                                  "            2       Lecithin          0.1                                    Cyclohexanol 1.5     --                                                       "            1.5     Sodium lauryl     0.01                                                        sulfate                                                  "            1.5     Lecithin          0.1                                    "            2       Sodium propyl     0.01                                                        sulfonate                                                "            2       Victawet 12 1.0                                          Atlas Chem Co G 263                                                                        2       --                                                       "            2       Sodium lauryl     0.01                                                        sulfate                                                  "            2       Victawet 12 1.0                                          ______________________________________                                    

Although this application has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible of numerous other applications which will be apparent topersons skilled in the art. The invention is, therefore, to be limitedonly as indicated by the scope of the appended claims.

I claim:
 1. In combination,a melt having properties of crystallizinginto a monolithic mass when nucleated, and a liquid additive material,in a weight to approximately ten percent (10%) by weight, havingproperties of occlusion in the growing crystals and exsolving toseparate the resulting crystallites and limit their size and ofcontrolling the temperature of the mixture during the time that the meltbecomes crystallized.
 2. The combination set forth in claim 1 whereinthemelt is a salt hydrate and the liquid additive material hasproperties of being dispersed throughout the salt hydrate melt.
 3. Thecombination set forth in claim 1 wherein theliquid additive material isselected from a group consisting of monohydric alcohols, diols andtriols.
 4. The combination set forth in claim 1 wherein theliquidadditive material has the properties of inhibiting the crystallizationof the melt during the time that the ambient temperature is below thefreezing temperature of water.
 5. The combination set forth in claim 3wherein themelt material is selected from a group including sodiumsulfate decahydrate, sodium thiosulfate pentahydrate, disodium hydrogenphosphate dodecahydrate, sodium acetate trihydrate, sodium chromatedecahydrate, calcium chloride hexahydrate, magnesium chloridehexahydrate, magnesium nitrate hexahydrate, urea/ammonium nitrate, andcalcium nitrate trihydrate.
 6. In combination,a melt having propertiesof melting at a particular temperature interval and of remaining in themelted state at temperatures below the particular temperature intervaland of being nucleated into a crystalline state as a monolithicaggregate at the particular temperature interval and of generating heatwhen nucleated into the crystalline state at the particular temperatureinterval, a liquid additive material having properties of being occludedin the crystals to subsequently exsolve and disrupt the crystals andprevent the crystals from growing beyond a particular size, and asurface active material having properties of reducing the surfacetension of the liquid additive material on the crystalline materialproduced from the melt.
 7. The combination set forth in claim 6whereinthe surface active material and the liquid additive material haveproperties of providing for the melting and crystallization of the phasesystem including the supercooled melt at substantially the particulartemperature.
 8. The combination set forth in claim 6 whereinthe surfaceactive material has hydrophilic properties and the liquid additivematerial has properties of being preferably adsorbed on specificsurfaces of the growing crystals and being occluded in the crystals tocontrol the texture of the crystalline aggregate in accordance with thechemical characteristics of the surface active material in thesupercooled melt.
 9. The combination set forth in claim 6 whereinthesurface active material is selected from a group consisting of sulfates,phosphates, phosphonates and sulfonates, and the liquid additivematerial is selected from a group consisting of monohydric alcohols,diols, triols, ketones and esters.
 10. The combination set forth inclaim 9 whereinthe melt is selected from a group consisting of sodiumsulfate decahydrate, sodium thiosulfate pentahydrate, sodium chromatedecahydrate, calcium chloride hexahydrate, magnesium chloridehexahydrate, magnesium nitrate hexahydrate, sodium acetate trihydrate,disodium phosphate dodecahydrate, urea/ammonium nitrate and calciumnitrate trihydrate.
 11. In combination,a melt having properties ofcrystallizing into a monolithic mass when nucleated, and a liquidadditive material, in a weight to approximately ten percent (10%),having properties of occlusion in the growing crystals and exsolving toseparate the resulting crystallites and limit their size and ofcontrolling the temperature of the mixture of the melt and the liquidadditive material during the time that the melt becomes crystallized,the liquid additive material being selected from a group consisting ofmonohydric alcohols, diols and triols.
 12. The combination set forth inclaim 11 whereinthe liquid additive material inhibits thecrystallization of the melt at temperatures below the freezingtemperature of water.
 13. In combination,a melt having properties ofcrystallizing into a monolithic mass when nucleated, and a liquidadditive material, to a weight of approximately ten percent (10%) in themixture, having properties of occlusion in the growing crystals andexsolving to separate the resulting crystallites and limit their sizeand of controlling the temperature of the mixture during the time thatthe melt becomes crystallized, the liquid additive material beingselected from a group consisting of monohydric alcohols, diols andtriols, the melt material being selected from a group consisting ofsodium sulfate decahydrate, sodium thiosulfate pentahydrate, disodiumhydrogen phosphate dodecahydrate, sodium acetate trihydrate, sodiumchromate decahydrate, calcium chloride hexahydrate, magnesium chloridehexahydrate, magnesium nitrate hexahydrate, urea/ammonium nitrate, andcalcium nitrate trihydrate.
 14. The combination set forth in claim 13whereinthe liquid additive material also inhibits the formation ofcrystals during the time that the ambient temperature of the mixture isbelow the freezing temperature of water.
 15. In combination,a melthaving properties of melting at a particular temperature interval and ofremaining in the melted state at temperatures below the particulartemperature interval and of being nucleated into a crystalline state asa monolithic aggregate at the particular temperature interval and ofgenerating heat when nucleated into the crystalline state at theparticular temperature interval, a liquid additive material havingproperties of being occluded in the crystals to subsequently exsolve anddisrupt the crystals and prevent the crystals from growing beyond aparticular size, and a surface active material having properties ofreducing the surface tension of the liquid additive material on thecrystalline material produced from the melt, the liquid additivematerial being selected from a group consisting of monohydric alcohols,diols and triols.
 16. The combination set forth in claim 15,including,the surface active material being selected from a groupconsisting of sulfates, phosphates, phosphonates and sulfonates.
 17. Thecombination set forth in claim 16, including,the melt being selectedfrom a group consisting of sodium sulfate decahydrate, sodiumthiosulfate pentahydrate, disodium hydrogen phosphate dodecahydrate,sodium acetate trihydrate, sodium chromate decahydrate, calcium chloridehexahydrate, magnesium chloride hexahydrate, magnesium nitratehexahydrate, urea/ammonia nitrate, and calcium nitrate trihydrate. 18.The combination set forth in claim 15 whereinthe liquid additivematerial has a concentration of approximately two percent (2%) to fivepercent (5%) by volume in the melt.
 19. The combination set forth inclaim 17 whereinthe liquid additive material has a concentration ofapproximately two percent (2%) to five percent (5%) by volume in themelt.
 20. The combination set forth in claim 19 whereinonly very smallamounts of the surface active material by weight are included in themelt.
 21. The combination set forth in claim 19 whereinthe amount of thesurface active material in the melt is considerably less than onepercent (1%) by weight.
 22. The combination set forth in claim 21whereinthe melt constitutes hypo and propylene glycol is included in arange to approximately ten percent (10%) by weight to control themelting temperature of the melt and to enhance the ability of the meltto continue as a liquid at temperatures below the melting interval.